A typical fuse is composed of two electric contacts, with a fuse element disposed therebetween and a casing made of an insulating material and adapted to house the fuse element and the connecting ends of the electric contacts to the fuse element.
When one of the electric contacts receives a current value exceeding a preset fusing current threshold, the fuse element melts and stops power supply to the power consuming unit connected to the other electric contact, thereby protecting it from current peaks.
Nevertheless, prior art fuses have an unsatisfactory operation at high overcurrent values, i.e. of the order of 8-10 times the rated current of the fuse.
Prior art fuses are disclosed, for instance in WO 03/075298, DE 10 2008 036672 and U.S. Pat. No. 4,751,490.
Particularly, at low overcurrent values, i.e. of the order of 1.35-6 times the rated current of the fuse, such fuses have melting times that remain within the maximum and minimum limits set by ISO standards. However, at high overcurrent values, i.e. of the order of 8-10 times the rated current of the fuse, they have an asymptotic behavior that does not ensure low operation times. In other words, at values of the order of 8-10 times the rated current of the fuse, the operation times, i.e. the melting times, remain substantially constant.
Therefore, it would be desirable to have fuses that can ensure low melting times both at low overcurrent values and at high overcurrent values, and particularly melting times that continuously decrease as overcurrent values increase.